Various types of chain saws are known having endless, closed-loop or ansiform cutting elements or bands. Such saws usually include a plate-like support member which carries and supports the endless cutting element, with the cutting element being driven generally about the periphery of the support member. A drive sprocket or the like is provided for drivingly-engaging the cutting element, with the motor of the saw acting to drive the sprocket for effecting high-speed movement of the cutting element for cutting operations. A motor means such as a pneumatic motor, a hydraulic motor, an electric motor, or an internal combustion engine is typically provided for powering the saw.
Various constructions are also known for chain saws, with a cutting element construction usually selected with consideration of the intended use of the saw. For example, some cutting elements comprise saw chains, which are particularly suited for efficient and high-speed cutting of wood, such as for logging and tree trimming. Other cutting elements include an endless array of planar cutting members hingedly-interconnected to form an articulated cutting blade, with relatively narrow kerf, which results from such articulated blades making, them particularly suited for use in the cutting of meat carcasses in butchering operations, or other cutting operations where narrow kerf and relatively low power requirements are important.
One problem encountered with chain saws is maintenance of the cutting element belt or chain for efficient and high-speed cutting. Naturally, such cutting elements must be periodically sharpened. This can be time-consuming, usually requiring removal of the cutting element belt or chain from the saw. Similarly, any failure of a cutting element can result in an undue interruption in work operations since the damaged element must be removed and replaced, which again can be undesirably time-consuming. As will be appreciated, facilities to repair or sharpen the saw may not be close at hand, such as during logging operations in the field. Since an interruption in work operations for saw maintenance is frequently unacceptable, it becomes necessary to bring a back-up saw, or at least back-up chains, to the work site. Of course, the need to maintain another entire saw ready for use significantly increases equipment and maintenance costs for performing the particular cutting operation.
As noted, chain saws having articulated cutting blades are particularly well suited for use in butchering operations. For such application, not only must articulated blades of such saws be properly maintained for efficient cutting, but such saws routinely must be thoroughly cleaned and sterilized to prevent undesired contamination of the meat products they are used to cut. Ordinarily, not only must the entire articulated cutting blade be cleaned but, additionally, the blade support and blade driving mechanism must be free of any matter which might spoil and/or cause contamination. Since a saw must usually be taken out of service for cleaning, back-up equipment is again required in order for butchering operations to continue.
For best performance, it is very important that the tension of the endless cutting element loop of a power-driven saw be properly adjusted. In the past, tension adjustment has typically been effected by providing an arrangement for displacing the cutting element support, e.g., the saw bar or blade support, of the saw with respect to the drive sprocket or the like which drives the endless cutting element. Such adjustment is usually made by altering the position of the cutting element support with respect to the motor housing of the saw after the support and endless cutting element construction have been mounted on the housing. See, for example, U.S. Pat. No. 4,382,334 to Reynolds. Although such arrangements can effect the desired tension adjustment, pre-tensioning of the cutting element loop is not possible. Also, it can again be time-consuming to adjust the cutting element tension each time the cutting element support is removed and reattached, thus detracting from efficient and convenient operation of the saw. Moreover, proper tension adjustment for optimum performance requires a skill that may not be readily available in the field.
In view of the above, it will be recognized that it is highly desirable to provide a power-driven saw with an easily-replaceble endless cutting element arrangement. Preferably, replacement of the cutting element arrangement should be possible in a minimum amount of time, preferably without the use of tools or the like. It is further desirable to provide an arrangement whereby the endless cutting element or chain for a saw can be selectively pre-tensioned. By providing a chain saw with a readily-detachable, pre-tensioned and replaceable endless cutting element or chain assembly which can be easily removed and replaced as a unit, cutting operations can be more efficiently and conveniently performed, with attendant savings in equipment maintenance time and expense.